Separation of inorganic anions for analysis of sea-water by capillary zone electrophoresis

A number of trace-level inorganic anions in sea-water have been separated efficiently by capillary zone electrophoresis using direct UV detection. The carrier electrolyte contained 100 mM KCl at pH 4.0, which offered the possibility of preventing interference from high matrix salinity and avoided the use of an additional flow modifier. As a result, no impact of the chloride ion on the migration of high-mobility anions was observed and short migration times (within 8 min) were obtained by operating at a relatively low applied voltage (–10 kV). Modifications to the carrier electrolyte composition by incorporating 18-crown-6 or tetrabutylammonium chloride were found essential for furnishing the appropriate resolution. The role of ion-association and ion-inclusion interactions, taking place in the electrophoretic system and resulting in variations of the separation selectivity, are discussed. The problem of improving the detection sensitivity for quantification of inorganic anions in sea-water is also briefly addressed.